This invention relates to a multilayer card-shaped data carrier having a core layer made of paper, and carrying an individualization by which it is associated with a person or an institution. In particular, the invention relates to payment cards, e.g. credit cards or bank cards, admission tickets, identification cards or data pages for passport booklets.
Particularly with cards individualized for persons or institutions, there is always the desire to secure them against forgery or tampering of any kind It is to be ensured that only authorized persons or institutions can manufacture and issue such identification cards.
WO 03/022598 A1 discloses for this purpose a card-shaped data carrier built up of a plurality of plastic layers, which carries on an inner layer a security element that can only be forged with great effort. In the cover layer located above the inner layer, a lenticular lens structure is moreover formed exactly over the security element. The domes of the lenticular lens structure rise above the surface and form elevated ribs. The lenticular lens structure produces a viewing angle-dependent optical effect. Depending on the configuration of the lenticular lens structure one can achieve different effects. There can be achieved, inter alia, the effect of an apparent motion or a color effect.
EP 323 108 A2 further discloses a multilayer card-shaped data carrier in the form of a security card whose upper side is configured as a lenticular lens structure over the full area. The lenticular lens structure here is so arranged that an individualization applied on an inner layer is recognizable only from a certain viewing angle.
DE 10 2009 004 128 A1 shows a data carrier which is based on a multilayer composite containing at least one paper layer. The data carrier is printed and furnished by embossing with a relief which, together with the print, produces a viewing angle-dependent effect. Printing and embossing can be carried out in an arbitrary order. In a variant, embossing-through is utilized as a security feature. This solution can be combined with holograms or other diffractive structures.
DE 44 41 198 A1 describes a card having a card body into whose upper side a lens structure is embossed. The lens structure thereby penetrates a lacquer layer applied to the upper side.
WO 2013/045055 A1 and EP 2173567 B1 disclose embossing in paper layers to manufacture security elements showing an optically variable effect.
The known solutions considerably increase the degree of difficulty in imitating accordingly equipped data carriers. However, they are suited primarily for plastic buildups. With multilayer buildups whose core layer is a paper layer, they do not offer any effective protection against attacks directed to separating the layer buildup in the paper layer. One known attack here consists in removing the cover layer together with any security elements located thereon, e.g. a lenticular lens structure, from the paper layer. If this succeeds, it becomes possible to tamper with individualizations, e.g. a statement of name or address, applied on the paper layer and now exposed. The previously detached cover layer together with its security elements can be re-applied to the tampered-with data carrier, so as to retain the security functions originally present.